Iron deficiency in early pregnancy using serum ferritin and soluble transferrin receptor concentrations are associated with pregnancy and birth outcomes.

Abstract

Background: There are several biomarkers for measuring iron deficiency (ID) in pregnancy, but evidence of their prevalence in association with inflammation and adverse pregnancy outcomes is inconclusive. Objectives: To describe the prevalence and determinants of ID in women in the first trimester of pregnancy and associations with pregnancy and birth outcomes. Design: A record-linkage cohort study of archived serum samples of women attending first trimester screening and birth and hospital data to ascertain maternal characteristics and pregnancy outcomes. Sera were analysed for iron stores (ferritin; μg/L), tissue iron (soluble transferrin receptor, sTfR; nmol/L) and inflammatory (C-reactive protein, CRP; mg/L) biomarkers. Total body iron (TBI) was calculated from serum ferritin and sTfR concentrations. Multivariate logistic regression analyzed risk factors and pregnancy outcomes associated with ID using the definitions: serum ferritin <12 μg/L, TfR ≥21.0 nmol/L and TBI<0 mg/kg. Results: Of 4,420 women, the prevalence of ID based on ferritin, sTfR and TBI was 19.6%, 15.3% and 15.7%, respectively. Risk factors of ID varied depending on which iron parameter was used and included maternal age <25 years, multiparity, socioeconomic disadvantage, high maternal body weight and inflammation. ID was associated with reduced risk of gestational diabetes (GDM) defined using serum ferritin and TBI, but not sTfR and increased risk of large for gestation age (LGA) infants defined using TBI only. Conclusions: Nearly 1 in 5 Australian women begin pregnancy with ID. Evidence suggests excess maternal weight and inflammation play a role in the relationships between ID and GDM and LGA infants.